Save and load user_data for p4est

[benegee]

This fixes restating when using AMR.
Resolves #1914

[github-actions]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.13%. Comparing base (8665300) to head (7b11b29).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1915      +/-   ##
==========================================
+ Coverage   95.93%   96.13%   +0.19%     
==========================================
  Files         460      460              
  Lines       36952    36956       +4     
==========================================
+ Hits        35449    35524      +75     
+ Misses       1503     1432      -71     

Flag	Coverage Δ
unittests	96.13% <100.00%> (+0.19%)	⬆️

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[ranocha]

Can we have a CI test for this?

[sloede]

Looks more or less good to me, I only have one small suggestion.

I also second @ranocha's request for a test (if possible).

[benegee]

I am still unhappy with this fix. While new_p4est allows to just allocate user data, load_p4est requires to also provide the data. So in the end I am only saving the data to have memory allocated upon restart.

I also do not know if there was a good reason for not saving user data in the first place.

[benegee]

The solution is to use p4est_reset_data!
cburstedde/p4est#308

[DanielDoehring]

So with this, is it possible to restart a simulation and refine the initial condition?

[benegee]

So with this, is it possible to restart a simulation and refine the initial condition?

Just checked with this example here and it seems to work.

[DanielDoehring]

Just checked with this example here and it seems to work.

Cool, thanks for picking this up!

[ranocha]

So with this, is it possible to restart a simulation and refine the initial condition?

Just checked with this example here and it seems to work.

Do we have a test for this? Or is it covered by the tests we already have?

[DanielDoehring]

Do we have a test for this? Or is it covered by the tests we already have?

So the newly introduced test does exactly this. So in some sense we "test for crash".

[benegee]

Thanks for your feedback!

Following @JoshuaLampert 's comment above and #1384 (comment) I removed ode_default_options() in elixir_advection_{extended,restart,restart_amr}.jl for p4est_2d_dgsem and tree_2d_dgsem.

In the new elixir_advection_restart_amr.jl for p4est_2d_dgsem and tree_2d_dgsem I set adapt_initial_condition = true. This still tests the restarting capability in general.

[JoshuaLampert]

Thanks!

[ranocha]

Thanks! However, some test tolerances are not satisfied right now: https://github.com/trixi-framework/Trixi.jl/actions/runs/9398803634/job/25884924262?pr=1915#step:7:2874

[benegee]

Thanks! However, some test tolerances are not satisfied right now: https://github.com/trixi-framework/Trixi.jl/actions/runs/9398803634/job/25884924262?pr=1915#step:7:2874

Yes! I wanted to update them, but it seems I also introduced some issue in the MPI test. I'm on it.

[benegee]

It seems to work now!